This is a 1970's painting of Old Tin Mine (see photo of similar by the same artist and photo of artist) in St. Agnes
by artist Ron Wood, born 1922 in London. He is not a listed artist (meaning known and collected), but he does have an impressive
biography of exhibitions and commissioned work of graphic art, sculptures and paintings (see here). This piece you have has
a current value of 500 to 700 British pounds.
Some sites that I recommend for selling are Varagesale.com, Ioffer.com, OfferUp.com, Ebay and letgo.com. I am not sure if all I've mentioned are also avaialable in the UK.
You can also go to invaluable.com or liveauctioneers.com and search their directory for an auction house near you and consign to them, which is usually best for fine art.
To finish, I will need you to click the five stars at the top of your screen and hit the submit button, thanks!